How did you fasten your solar panels?

[ShrimpBurrito]

I’m considering putting a 360 watt solar panel on the rear shell of my 2720SL, measuring roughly 66 x 40” and weighing about 40 lbs. I’ve read that a number of folks have attached the panel to the roof for various VHB tapes, but I want to use a mechanical fastener in addition to some sort of adhesive.

Northern Arizona Wind and Sun - a very reputable solar dealer - has told me they’ve received reports from RV owners where VHB tape has failed in this setting, and the solar panel subsequently departed the roof. Obviously, very dangerous and potentially life-threatening, and ultimately, the strength of the joint will also depend on the strength of the bond between the aluminum and paint (unless the paint is removed). They use these brackets:

https://www.solar-electric.com/mse-module-mounting-kit.html

...which I think is basically a simple Z-bracket with a strip of butyl tape on the bottom, and then put lap sealant over it. In addition to the tape, they use 3 #14 sheet metal screws at each bracket, and reportedly, have never had a failure.

Of course, I’m guessing most of their installs are on conventional RVs with rubber roofs with an underlying plywood, and so that would be great, though they did say they’ve done installs on Airstreams. But TMs have no such plywood, and so the screws would literally be just held by the thin sheet metal. But, with at least 12 screws holding in the panel, maybe that would be adequate?

I’ve also considered well nuts and rivet nuts. I understand well nuts are often used by OEM manufacturers to attach roof racks to cars, so that seems like a good proof of concept, but they also require a large hole, and I’m not sure there would be enough room or holding power with 3 holes places so closely together in a typical bracket. I could build my own bracket of course with some stock z-channel....

Does anyone know where the framing is in the TM roof? I presume it’s only along the edge, but I don’t know.

How did you fasten your solar panels to the roof?

Dave

[rickst29]

Completely re-written, eliminating the VHB tape option. His large panel can generate considerable "lift" force during travel.

AFAIK, although it may have changed after my model year - the "structure" of the shells is only the foam and aluminum sandwich, with foil-covered plywood along the edges. Probably use SS screws all the way through the roof for each Z bracket. On the inside, with fairly 1" washers to spread the force of the screw and nut onto a wider area of aluminum sheet ceiling, and then small nuts (nylon sleeved "self-locking' type) below the washer. After drilling, but before mounting the Z-brackets and inserting the screws, I would fill each screw hole with 3M-5200 boat sealant and also paint the underside of the Z-bracket with the same stuff. When tightened, that will provide excellent waterproofing - wipe away the excess which gets pushed out (forming a caulk-like seal along the edges of the Z-brackets, and also at the screw entry into the roof).

Inside, I'd wipe off everything which gets squeezed around the washer. Then I'd hacksaw any remaining screw length which extends past the nut. I'd use nylon sleeved 'self-locking' nuts in this application - If anything ever feels loose (and it probably will need some tightening after the roof sandwich settles a bit) the screws can be tightened from the outside top, and the nuts shouldn't move.

[ShrimpBurrito]

Thanks, Rick!

Anyone else? Rick can’t be the only one with solar panels!

Dave

[rickst29]

And I have the wrong kind (mine are all semi-flexible, for which VHB tape is perfect). But I used to have glass-framed, like yours. I re-wrote the preceding post, now recommending screws only.

And I'd also suggest that you try to avoid drilling holes near the edges, or into the center joint, because there might be nearly wires attached to wood framing in those areas (the interior ceiling lights, and the exterior Bargman connected lamp wires for running lights/break lights/backup lights).

[lederhos]

I’ve had good luck with 1” VHB tape between a 2’ piece of 1 1/4” angle aluminum on each side of 100 watt panels. When I went to remove them after 10 years, I had one heck of a time (fishing line will be used if I ever have to repeat). If I decide to go back to ridged panels I will use the same method even if much larger panels. I might use longer channel and will silicon around it not for sealing but to keep UV from degrading the VHB tape from the sides. If I was REALLY concerned I MIGHT pin each end of the channel with one sizable pop rivet through the top “skin” only and with appropriate sealant, just to prevent a possible lift from starting at the ends. I would avoid using fasteners that “sandwich” the roof.

[ShrimpBurrito]

Thanks, Eric. That’s the kind of method I am leaning towards, though I can’t get a 2-foot section of angle iron to lie flat on the roof because the roof is curved, both to the side and front-to-back, towards the back of the rear shell (which is where I want to put the panel). I’m looking at a panel roughly 66 x 40, which is about the size that most panels are these days, I’m finding, outside of a Renogy and a few off-brands. But the best performing and highest rated panels are bigger. From what I’ve heard, this is a recent industry trend....just a few months ago I could easily find good smaller 200-watt panels, but no longer.

So I’m curious — why did you decide to remove your panels? You indicated that if you “got back to rigid panels” you would use the same method, so did you go flexible? I still am not completely settled on my design yet, and would love to hear your plan and reasoning.

Thanks!
Dave

[ShrimpBurrito]

Thanks, Rick, that’s an interesting idea. I called both the factory and our local Trailmanor dealer, and I was surprised to find that, in both cases, they install panels with brackets (probably the Renogy brackets) that have 2 holes each with just sheet metal screws, and then put either silicone or lap sealant around the bracket, and call it a day. Wow. Northern Arizona Wind and Sun uses a bracket with butyl tape attached (much like what is used to attach the roof vents) as well as some sheet metal screws with some unusual type of lock washer.

In any event, while I know these panels are likely smaller than mine, all I would need to do I think is add more brackets, and if I wanted more security (and I think I do), I could also put in some strong pop rivets as Eric suggested.

Dave

[rickst29]

Lots of people have had leaks when they're put under stress (e.g. the factory awning mounts). If not the mere VHB tape, I would still prefer to go all the way through and "sandwich" both of the sheet metal layers.

[lederhos]

Dave, I removed the ridged panels to reduce weight and to try flexible panels. Last year I went with a new version of Renogy 160 watt panels that did not even make it a year. Two failed with in 9 months. Mounting was according to manufacturer specifications and the panels seemed very durabl, certainly enough to last for years, but formed corrosion marks at several points along the bus bars. If I go back with flexible, I may go with the shingle style recommended by rickst29 or more likely CIGS panels like the 80 watt panels from richsolar. They are pricey for the wattage, but meet mil specs and are one of the most durable flex panels on the market. They also happen to fit the roof space on the back shell of my 3124 perfectly. These panels went for more than $1000/ea only a couple years ago. Hoping to see another price drop before I need them.

[lederhos]

If you desire to go with ridged panels an easy way to get the angle aluminum to fit the contour of the roof it to cut several slits down through the vertical side all the way to the flat side that is taped to the roof. This will allow the side taped to the roof to flex with the contour of the roof. Again, I had extremely good success with VHB, but this assumes both surfaces are prepped correctly and the tape is not exposed to UV. Weather exposure had no discernible effect on the tape

[jessicatcampos]

My setup includes a blend of Z-brackets, rivet nuts, and lap sealant, combined with an energy storage system from Ace Battery. So far, the system has been rock solid without any issues.

[Wavery]

I've been using Z brackets held down with 3M VHB tape for years, on many different rigs. 3 different TrailManors, Coleman pop-up (aluminum roof) and 2 different motorhomes (fiberglass Roofs). I've towed for thousands of miles under every weather and wind condition imaginable. With the motorhomes (with large solar panels) I regularly drove 75mph.

In my opinion, if someone had a failure with VHB tape, there must have been an application error. A common error would be improperly preparing a sound surface by not cleaning thoroughly with soap and water, let dry, clean well with 70% rubbing alcohol on the roof AND the Z brackets (to remove manufacturer oils etc).

I would not recommend using VHB tape on a rubber roof or a painted roof (holding power is limited the the holding power of the paint). TrailManor roofs are anodized (not painted) and hold very well when prepared properly.

If you decide to go with thru-bolting the panels with an interior backing plate or large washers, I'd recommend that you install 1" long "crush-sleeves" between the layers of aluminum to prevent smashing the interior Styrofoam.


Well nuts or rivnuts are a better solution than thru-bolting IMO. However, VHB tape (properly installed) has a higher holding power. I just finished helping a friend install a solar panel rack on his Class a motorhome. The 165"x 88" rack sits 12" off of the roof (above the air conditioners) and there are 4, 385W solar panels on it. There are 6, legs with 15" long aluminum feet. Each foot is held to the fiberglass roof with (properly prepped) 1.5" x 15" VHB tape. Each leg has holding power of 1575# x 6, legs = nearly 10,000#.

Besides all that......... a solar panel mounted on the rear roof of the TM, sees very little wind resistance.

[ShrimpBurrito]

I think I must have posted this elsewhere, but I ended up using VHB tape also. Instead of Z-brackets, I used "Sticky Feet":

https://rvsolarstore.com/index.php?route=product/product&keyword=sticky&category_id=0&product_id=112

They're far more expensive that z-brackets (though not as much as they are now when I bought them), and are probably overkill, but it made installation on the uneven surfaces of the roof a breeze. Further, the panels are easily removed. They're not special -- just some machined aluminum, and they could easily be fabricated elsewhere. It's just a matter of work!

After I stuck the panels down with the tape, I applied some flexible caulk around each bracket to prevent exposure of the tape to the elements, though I'm not sure that's necessary. They've been on about 18 months now, and they're still rock solid. I'm happy.

Picture attached.

Dave